fix: allow multiple optional parameters with defaults (#12070)

* fix: allow multiple optional parameters with defaults

* Apply suggestions from code review

* partial fix

* feat: parse as a whole function

* couple of fixes

* work around acorn-typescript quirks

* add the harder test

* Update .changeset/ten-geese-share.md

---------

Co-authored-by: Rich Harris <hello@rich-harris.dev>
Co-authored-by: Rich Harris <rich.harris@vercel.com>

.changeset/ten-geese-share.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: allow multiple optional parameters with defaults in snippets

packages/svelte/src/compiler/phases/1-parse/acorn.js

@@ -1,6 +1,7 @@
 import * as acorn from 'acorn';
 import { walk } from 'zimmerframe';
 import { tsPlugin } from 'acorn-typescript';
+import { locator } from '../../state.js';
 
 const ParserWithTS = acorn.Parser.extend(tsPlugin({ allowSatisfies: true }));
 
@@ -127,6 +128,16 @@ function amend(source, node) {
 			// @ts-expect-error
 			delete node.loc.end.index;
 
+			if (typeof node.loc?.end === 'number') {
+				const loc = locator(node.loc.end);
+				if (loc) {
+					node.loc.end = {
+						line: loc.line,
+						column: loc.column
+					};
+				}
+			}
+
 			if (/** @type {any} */ (node).typeAnnotation && node.end === undefined) {
 				// i think there might be a bug in acorn-typescript that prevents
 				// `end` from being assigned when there's a type annotation

packages/svelte/src/compiler/phases/1-parse/state/tag.js

@@ -3,6 +3,7 @@ import read_expression from '../read/expression.js';
 import * as e from '../../../errors.js';
 import { create_fragment } from '../utils/create.js';
 import { walk } from 'zimmerframe';
+import { parse_expression_at } from '../acorn.js';
 
 const regex_whitespace_with_closing_curly_brace = /^\s*}/;
 
@@ -268,39 +269,28 @@ function open(parser) {
 			e.expected_identifier(parser.index);
 		}
 
-		parser.eat('(', true);
-
-		parser.allow_whitespace();
-
-		/** @type {import('estree').Pattern[]} */
-		const parameters = [];
+		let slice_end = parser.index;
 
-		while (!parser.match(')')) {
-			let pattern = read_pattern(parser, true);
-
-			parser.allow_whitespace();
-			if (parser.eat('=')) {
-				parser.allow_whitespace();
-				const right = read_expression(parser);
-				pattern = {
-					type: 'AssignmentPattern',
-					left: pattern,
-					right: right,
-					start: pattern.start,
-					end: right.end
-				};
-			}
+		parser.eat('(', true);
 
-			parameters.push(pattern);
+		let parentheses = 1;
+		let params = '';
 
-			if (!parser.eat(',')) break;
-			parser.allow_whitespace();
+		while (!parser.match(')') || parentheses !== 1) {
+			if (parser.match('(')) parentheses++;
+			if (parser.match(')')) parentheses--;
+			params += parser.read(/^./);
 		}
 
-		parser.eat(')', true);
+		let function_expression = /** @type {import('estree').ArrowFunctionExpression} */ (
+			parse_expression_at(
+				parser.template.slice(0, slice_end).replace(/\S/g, ' ') + `(${params}) => {}`,
+				parser.ts,
+				0
+			)
+		);
 
-		parser.allow_whitespace();
-		parser.eat('}', true);
+		parser.index += 2;
 
 		/** @type {ReturnType<typeof parser.append<import('#compiler').SnippetBlock>>} */
 		const block = parser.append({
@@ -313,10 +303,9 @@ function open(parser) {
 				end: name_end,
 				name
 			},
-			parameters,
+			parameters: function_expression.params,
 			body: create_fragment()
 		});
-
 		parser.stack.push(block);
 		parser.fragments.push(block.body);
 

packages/svelte/tests/parser-modern/samples/snippets/output.json

@@ -32,20 +32,28 @@
 						"loc": {
 							"start": {
 								"line": 3,
-								"column": 14,
-								"character": 43
+								"column": 14
 							},
 							"end": {
 								"line": 3,
-								"column": 25,
-								"character": 54
+								"column": 25
 							}
 						},
-						"end": 54,
+						"end": 46,
 						"typeAnnotation": {
 							"type": "TSTypeAnnotation",
 							"start": 46,
 							"end": 54,
+							"loc": {
+								"start": {
+									"line": 3,
+									"column": 17
+								},
+								"end": {
+									"line": 3,
+									"column": 25
+								}
+							},
 							"typeAnnotation": {
 								"type": "TSStringKeyword",
 								"start": 48,

packages/svelte/tests/parser-modern/samples/typescript-in-event-handler/output.json

@@ -54,7 +54,10 @@
 											"line": 6,
 											"column": 12
 										},
-										"end": 87
+										"end": {
+											"line": 6,
+											"column": 25
+										}
 									},
 									"name": "e",
 									"typeAnnotation": {

packages/svelte/tests/runtime-runes/samples/snippet-optional-arguments-defaults/_config.js

@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	html: '013/023'
+});

packages/svelte/tests/runtime-runes/samples/snippet-optional-arguments-defaults/main.svelte

@@ -0,0 +1,9 @@
+{#snippet one(a, b = 1, c = (2, 3))}
+  {a}{b}{c}
+{/snippet}
+
+{#snippet two(a, b = (1, 2), c = 3)}
+  {a}{b}{c}
+{/snippet}
+
+{@render one(0)}/{@render two(0)}